For those wishing to theme Whiskermenu... in gtk3, here is an example theme. I have made it so that it compliments the POP! Theme nicely (from system76). Hopefully it will give folks a useful template to edit and customize for their own purposes.
This file should be placed in your /home/username/.config/gtk-3.0 folder as gtk.css:
/* bottom of the main body area */
#whiskermenu-window {
background-color: #393634;
color: #E5E5E5;
}
/* Make sidebar buttons match */
#whiskermenu-window button {
background-color: #574F4A;
color: #F1E9E9;
}
#whiskermenu-window button:hover {
background-color: #B0710B;
color: #FFA500;
}
#whiskermenu-window button:checked {
background-color: #574F4A;
color: white;
}
/* main body area */
#whiskermenu-window treeview:hover {
background-color: #F3E8D4;
color: #251212;
}
#whiskermenu-window treeview {
background-color: #F9F9F9;
color: #1a1a1a;
}
/* whiskermenu outer border */
#whiskermenu-window border {
background-color: #574F4A;
border-color: #4C4845;
}
Just log out and login to see the changes...